Hologram recording methods so far developed include the one disclosed in Patent Document 1. In the method disclosed in this document, an recording beam is emitted perpendicularly to the hologram recording medium while a reference beam is emitted to the region irradiated by the recording beam at different incident angles by controlling the inclination of a multiple mirror. The multiple mirror is inclined about a fulcrum supported by a support member, which is movable in parallel to the hologram recording medium. The incident angle of the reference beam onto the hologram recording medium is changed according to the inclination of the multiple mirror, in which process the multiple mirror is moved parallel to the hologram recording medium so as to position the reference beam on the region to be illuminated. Under such configuration, the recording beam and the reference beam interfere in the illuminated region, so that the holograms are recorded in multiple according to the intersection angle between the recording beam and the reference beam.
With the conventional hologram recording method cited above, however, in the case where the incident angle of the reference beam onto the hologram recording medium is increased, the illumination width of the reference beam is increased according to the illuminance cosine law, which inevitable leads to an increase in area of a portion not superposed on the recording beam. In other words, an unnecessary exposure region irradiated only by an surplus portion of the reference beam is created on the end portions of the illuminated region, which constitutes a unit recording region where the holograms are to be recorded in multiple, and such unnecessary exposure region becomes larger in accordance with the incident angle of the reference beam. This makes it necessary to provide a large spacing between the adjacent unit recording regions in order to keep the unnecessary exposure regions, where only the reference beam is present, from overlapping, which imposes the disadvantage that the recording density cannot be enhanced.